Insulating telephonic relay



Sept. 2, 1930. F. c. DOBLE 1,174,.745

INSULATING TELEPHONIC RELAY Original Filed Aug. 2, 1920 A A A A A A A A AAAAAAAAAA vvvvvvvv vvvvv vvvvv Even $02 %rww$ 6 $0630,

w www Patented Sept. 2, 1930 UNITED STATES PATENT GFFICE FRANK C. DOBLE, F CAMBRIDGE, MASSACHUSETTS INSULATING TELEPHONIC RELAY The present invention relates to a transmission device or relay between telephone lines adapted to connect telephonic instruments in, such lines acoustically, but to insulate them electrically from one another. One use for such a relay or insulating acoustical connection is to transmit speech between a low tension telephone system and a high tension system. The term high ten sion, as here used in connection with telephone systems, means those which are provided'in connection with or near lines for the transmission of electrical power at high ten-. sion. In such cases, a direct electrical con- '15 nection between the two lines might be highly dangerous to users oi the low tension line, but by interposing a sound conducting connection which is also an insulator of electricity between instruments in the two lines, direct transmission of speech and other sounds from one line to the other is accomplished without danger.

The invention consists in the means andcombinations adapted to accomplish the objects and results above outlined, substantially as set forth in the following specification, and in equivalent structures and combinations.

This invention was first disclosed and claimed in my application filed August 2, 1920, Serial No. 400,7 411, on which patent was granted June 9, 1925, No. 1,541,121, entitled Insulating medium for transmission of intelligible sounds, and the presentapplication is a division of that above named.

In the drawings which accompany this specification,'

F1". 1 1s a dia ram illustratm the )rmci- I e a I p h a ples oi my invention as applied in a form 40 which includes asingle insulating sound con- 400,741. Patent No. 1,541,121, dated June 9, 1925. Serial No. 35,438. Renewed February 4, 1930.

transmission medium adapted to serve as a relay in the combination illustrated in the preceding figures.

Like reference characters designates the same parts wherever they occur in all the figures.

The ordinary telephone lines and systems, such as are in wide and general public use, are low tension systems in which the potential of the actuating current is so'near the earth potential that there is no danger to persons using the instruments in such systems of being harmed by current discharges therefrom, except in exceptional or accidental circumstances. But there are other telephone systems, called high tension systems, of which the line wires are run in close proximity to transmission lines carrying electric power at high potential, and such systems are liable to receive high potential charges either directly or inductivelyi'rom the adjacent power transmission line, of a nature and from causes well known to those acquainted with the art.

Although many circumstances exist wherein it is desirable to transmit speech between telephone lines of these two systems, it is not advisable to do so electrically on account of the great danger of personal injury to the user of the low tension line, while it is practically impossible to do so because of laws or regulations which prohibit a direct elec trical connection being made between high tension and low tension telephone lines. In order to permit t transmitting sounds between such lin-es, while at the same time insulating them from one another, I have devised a sound transmitting and insulating medium, in combination with a telephonic sound receiver in one line and a telephonic sound transmitter in the other line, or between receivers and transmitters, respectively, in both lines. The said medium is illustrated in detail in Fig. 3, and consists essentially in a tube a of any insulating or non-conducting substance which has suitable insulating value and it may be made in any length sufficient to prevent passage of current from one line to the other under even the highest voltage liable to occur either line, S i medi m is also made with a suitable ratio of bore diameter to length for transmitting sound, including articulate speech, clearly and distinctly. As indicating suitable ratios, I may say that I have found that tubes with a bore of onehalf an inch and lengths from three to ten feet, and those of a bore of three fourths of an inch and lengths t 0111 ten to twenty feet, give excellent results in this respect. Tubes of these dimensions, as well as oil other specific dimensions and similar ratios, may be made of wood, or of hard or flexible rubber, and of other insulating materials, by known manufacturing methods. \Vhcn the material used is wood, I pre'lier to make it repellant to water, as by impregnation with para'tlin, in order to avoid danger of its insulating value becoming lessened by absorption of moisture, whether in the form oi water vapor in humid air, or of liquid water lodging directly on the tube.

The manner and combination in which such sound transmitting medium is used for the purposes of the present invention is illustrated diagrammatically in Figs. 1 and 2. Referring first to Fig. 1, L and L represent the line wires of two telephone systems. Either of these lines may be considered as a low tension line and the other a high tension line; or both may be high tension lines without departure from the essence of the invention. The sound transmitting insulating tube a is interposed between a telephonic receiver 5 connected to one of the lines, and a telephonic sound transmitter 0 connected to the other line. In this description and in the following claims, the term receiver means any device which is capable of transforming electrical impulses or undulations into sound waves, and the term transmitter means any device apable ol" trans'torn'ling sound waves into electrical undulations or impulses capable of being carried electrically. In other words, these terms are used with generally the same significance as in common parlance respecting telephonic instruments. and with comprehensive inclusion of any in.- struments or devices having the same purpose and result. It is not necessary to describe the mauner and means by whicn the receiver and transmitter are connected to their respective lines, because any mode of connection already known in the art may be used; while reterence to my parent patent is directed for a description of connections, with suitable protection, such as are used in the ordinary bridging telephone set.

The sound conducting medium a is arranged and held with its opposite ends in such proximity to the receiver and transmitter, respectively, that sounds emitted by the former are conducted to the latter. It may be assumed that suitable sup wrting or attaching means will be used to hold the sound conducting medium in proper register and connection with the terminal instruments (the receiver and transmitter) respectively. In the arrangement as shown in Fig. 1, speech and other transformed sounds transmitted electrically by the line L will be carried across in the form of sound waves from the receiver 6 to the transmitter c, and there reconverted into electrical undulations and carried over the line L.

Fig. 2 shows a diagram in which not only a receiver 7) in line L is connected to the transmitter c in line L by a sound connector a, but also a transmitter 0' in line L is connected with a receiver 5 in line L by a similar sound connector a. Then operators using the respective lines at distant stations may hold a conversation with one another through the two channels of the relay. \Vhereas the relay shown in Fig. 1 contains a single sound channel between one receiver and one transmitter, that in Fig. 2 has two channels adapt ed to transmit sound in respectively opposite directions between a receiver in each line and a transmitter in the other.

Thus my invention enables speech to be transmitted between more or less remote stations on the different lines without putting either the low tension system or its users in danger from the high potential conditions which are liable to occur in the high tension system. The conduits or tubes a and a, in either case, may be made long enough to obtain the needed insulating effect. They may be constructed of separate lengths joined together end to end when great length is required; and they may be grounded, if desired, for additional protection, from any point and in any use where grounding would be an additional safeguard to the operator or the apparatus. It is to be understood also that the lines, and the telephonic, or other, apparatus in each line, are separated each from the other by a distance so great that there is no liability of an electrical discharge occurring from one to the other through the air insulation between them.

I wish it to be clearly understood that the fundamental idea of this invention is not limited as to the particular construction of the transn'iitters, receivers or other electrial sound converting devices which may be used in the combination here illustrated and in connection with my sound conveying insulating medium. Furthermore, such me dium, while being a tube in the sense that it contains a channel or bore, may have any form which enables it to conduct sound intelligibly. The term tube as herein used, includes any hollow body or shell having a passage adapted to conduct sound waves through it, whether such shell and passage are regular or irregular in shape and dimen sions. The tube is additional to the electrical apparatus proper and is an insulating protector capable of preventing flow to the ground of high tension electrical potential from. the high tension line. To be an insulating protector within the meaning of this specification, the medium or tube must be capable of withstanding, without breaking down, a sustained electrical stress of at least 1000 volts pressure (root mean square sine wave value) at any frequency.

WVhat I claim and desire to secure by Letters Patent is:

1. The combination, with two electrically separated telephone lines and a telephonic transmitter and receiver connected in the respective lines, of an insulating sound conducting means extending between said transmitter and receiver and adapted to conduct sound between them while providing insulation against the flow of electric current from one to the other under an electromotive force of at least 1000 volts.

2. The combination, with two telephone lines, one of which is a high tension line, and a telephonic receiver in one line and a telephonic transmitter in the other line, said lines, and the receiver on the one hand and transmitter on the other hand, being electrically disconnected and separated from one another by a distance sufficient to prevent discharge from one to the other of high tension electrical potential, of a sound conducting tube which is also an electrical insulator having equivalent insulating value, extending between said receiver and said transmitter in such relation thereto as to conduct sound waves from the former to the latter.

8. The combination, with two telephone lines, of a receiver in one line, a transmitter in the other, and a tube extending between said receiver and said transmitter; said tube being adapted to conduct sound waves from the receiver to the transmitter of an intensity and clarity suiiicient for the conversion thereof by the transmitter into electrical undulations capable of being delivered as intelligible sound by a distant receiver in the line; said tube being of insulating material and capable of preventing flow of high tension electrical potential of at least 1000 volts from one line to the other.

4. The combination, with two separate telephone lines and telephone instruments in the respective lines, each having a receiver and a transmitter, said lines and instruments being electrically insulated from one another, of sound conductors leading from the receiver of each line to the transmitter of the other, and adapted to conductsound between the two lines, said sound conducting means being made of insulating material and having a length suflicient to prevent discharge of high tension electrical potential of at least 1000 volts from one line to the other.

5. The combination, with two separate apparatus for the electrical transformation and transmission of sound, one of which is liable to receive high potential electrical charges. and one of them including a transmitter and the other a receiver, said apparatus and their receiver and transmitter being electrically insulated from one another by air insulation and otherwise of an extent suflicient to prevent discharge from one to the other of an elect ical charge at a potential commensurate with that of a high tension electrical power transmission line; of a sound conducting tube extending directly between said receiver and transmitter, made of insulating material and having a length and insulating value sufficient to withstand an electrical stress of the value hereinbefore stated.

In testimony whereof I have affixed my signature.

FRANK C. DOBLE. 

